We continue to study the sensitivity and specificity of placental proteins, chorionic gonadotropin and its free alpha and beta subunits (CG-beta), placental lactogen, and pregnancy-specific beta1-glycoprotein (SP1) as cancer markers in vivo and in vitro. Alpha and CG-beta may be useful markers for certain malignancies, notably islet cell carcinomas of the pancreas. SP1 is produced in vivo by certain non-seminomatous germ cell tumors of the testis. Ectopic production of SP1 in vitro has been demonstrated in a number of malignant cell lines and was particularly high in a line derived from a fibrosarcoma.